This invention relates to franking machines and in particular to the provision of facilities to enable communication between such machines and other devices for the transfer of data.
In order to prevent fraudulent use of franking machines, the electronic circuits for carrying out accounting functions and for registering data relating to transactions carried out by the machine are housed within a secure casing to prevent unauthorised access to the circuits. Commonly, means are provided to prevent unauthorised transactions which, in the event of attempted fraudulent use, render the franking machine inoperative. The machine then has to be returned to a service depot for validation of the data stored in the electronic circuits and to be rendered operative for franking operations once again.
For use with postal authorities which require prepayment for franking, the franking machine is provided with means to receive a value of credit available for franking which, in the course of subsequent franking operations, is decremented by the value of franking effected. When the credit value is less than the intended value of franking, the franking machine or at least that part containing the accounting and register circuits needs to be taken to the postal authority for the entry of further credit. In order to permit this authorised entry of credit, the machine is provided with means such as a switch located behind a sealed access for operation by the postal authority to place the accounting and control circuits in a state to accept and register the credit. After updating the credit the access is re-sealed by the postal authority to prevent unauthorised credit updating. It has also been proposed to update credit remotely, without the necessity of returning the machine to the resetting authority, by using the telephone to communicate data from the postal authority to the user to enable the user to enter the updated credit. This is accomplished by orally informing the user of a code which contains, in encrypted form, data relating to that specific machine and to the current update of credit. The user then has to key in on the keyboard of the machine the code communicated to him and, provided the code is validated by the machine, the new credit amount is added to that registered by the machine.
Thus it will be appreciated that the only permitted access to the machine for a user is by means of the keyboard. As a result transfer of data into and out of the franking machine previously required the intervention of an operator to key in the data or to read data from a display on the machine.
The need for an operator to key in a code which, because it has no logical meaning to the operator, is liable to be keyed in with errors has been overcome by systems for secure transmission of information used in updating of credit data in a franking machine disclosed in U.S. Pat. No. 4907271. In one of the systems disclosed therein, the data is stored in a portable member which has an electronic storage device contained in it and the franking machine is provided with an electrical connector which allows a user to connect the portable member to the internal circuits of the franking machine. To prevent fraudulent alteration to the data stored in the portable member, the data is stored in encrypted form which may use a code unique to that franking machine. The internal circuits of the franking machine include decoding algorithms and circuits responsive only to correctly encrypted data to allow updating of credit data in the registers of the franking machine. In another of the systems disclosed in U.S. Pat. No. 4907271 the franking machine is connected via a modem with Post Office equipment over a communications link such as a telephone system, the modem connecting the franking machine to the telephone network being plugged into the connector provided in the franking machine housing. Fraudulent updating of the credit data in the franking machine is prevented by encrypting the secure data prior to transmission from the post Office equipment. The encryption of the data also prevents fraudulent entry of data by the application of electrical signals directly to the contacts of the connector of the franking machine. The transfer of data as described hereinbefore is concerned with secure data such as data relating to credit held in a descending register. Furthermore transfer of other encrypted data such as the accumulated value of franking held in an ascending register and transaction code data may be transferred from the franking machine by reading such encrypted data out into the storage device of the portable member or for transmission over the telephone system. In addition to transfer of secure data it is also desirable to be able to transfer non-secure data to and from the franking machine. For example it may be desired to connect a weighscale to permit the input of signals from the weighscale indicating the value of franking, dependent upon the weight of a mail item, to the accounting circuit. Another example is the output of signals from the franking machine to a printer to maintain a hard copy tally of franking transactions. Such signals do not represent data utilised in accounting for use of the franking machine upon which payment for such use is based. Accordingly there is no requirement to prevent tampering with these signals and the data represented thereby is considered to be non-secure data.
It would be convenient for credit updating to the registers in the machine, for providing data on the status of the registers in the machine to the postal authority and for transfer of non-secure data to be able to provide means whereby transfer of data could be carried out not only by use of the portable member referred to hereinbefore but also by direct electrical connection of the franking machine with other devices.
However a difficulty arises because the devices which it is desired to connect to the franking machine may operate to communicate data using different interface standards. For example some devices may operate to the so-called RS232 standard, some devices may operate to the so-called RS422 standard and other devices may operate to other standards such as current loop, standards specific to particular manufacturers of such devices, or even in the future may be designed to operate to standards which have not yet been devised. As a result it has been necessary to construct the franking machine with an interface designed specifically for communication with devices operating to only one standard. Accordingly whenever communication is desired with a device operating to a different standard, a different specific interface must be built into the franking machine. This is particularly inconvenient in relation to franking machines because each and every different design and construction of franking machine must be submitted for evaluation and approval to the relevant postal authorities before those machines may be marketed for use by customers. This is an inconvenient and time consuming operation and when new devices become available and are desired to be used by connection with a franking machine, if they operate to a new communication standard, they can only be used after the inevitable delay involved in designing and obtaining approval for the franking machine with an interface operating to the new standard.